The present invention relates to a no-break power supply apparatus in which a plurality of constant-voltage constant-frequency power supplies having inverters constructed of gate turn off thyristors and gate control circuits therefor are operated in parallel.
In a constant-voltage constant-frequency power supply (hereinafter abbreviated as to "CVCF") in a conventional no-break power supply apparatus, it was indispensable to provide thyristor breakers at the output side, and when a D.C. shortcircuit occurred due to commutation failure in one of the inverters which were operated in parallel, the thyristor breaker was operated to disconnect the failed inverter from the power supply and a load, and a power was supplied only from the proper inverters to the load. However, the thyristor breakers were expensive, and since a plurality of inverters were operated in parallel, it had the drawback that the entire apparatus has become even more expensive because an inverter had to be provided for each power supply.